The present invention relates to machine tools, and, more particularly, to machine tools in which the machining head is moved in multiple axes relative to the workpiece.
In laser cutting installations and other machining operations involving large plate-like workpieces, it is common to support the workpiece on a worktable and to effect relative movement between the machining head and the workpiece. Although the worktable can be moved relative to the machining head, generally it is preferable to mount the machining tool on a support located above the workpiece and to move the support with the machining head thereon relative to the workpiece in both X and Y axes under computer control. Typically, the support for the machining head is a bridge which extends between the side rails and on which it is movable relative to the workpiece on one axis. Moreover, the machining head is generally supported on the bridge so that it is movable along the length of the bridge thus providing relative motion of the machining head in both X and Y directions.
As will be readily appreciated, the bridge is a substantial structure with a relatively large mass so that motion of the bridge in the one axis requires substantial power to overcome the inertia and to effect the continued motion. The power for movement in the transverse direction is much less because the machining head is lighter and it moves along the length of the bridge.
Because of the large mass and the need to start and stop the motion of the bridge, the cutting action of small intricate contours may not be as precise as is desirable, and the costs and wear of the drive system for the bridge can adversely effect the economics of the types of parts to be processed in a particular machine tool installation are small and of intricate configuration.
Accordingly, it is an object of the present invention to provide a novel machine tool in which the motion required of a substantial bridge or like support may be substantially reduced.
It is also an object to provide such a machine tool in which the quality of the machining of small intricate contours is improved.
Another object is to provide such a machine tool which can be fabricated readily and which is relatively simple to operate.
It has now been found that the foregoing and related objects may be readily attained a machine tool for machining workpieces by motion of the machining tool relative to the workpiece comprising a worktable having X and Y axes and adapted to support a workpiece thereon, and a support extending transversely above the worktable in the X-axis and movable along the Y-axis of the worktable. First machining tool mounting means is movably mounted on the support for movement along the support in the X-axis, and second machining tool mounting means is movably mounted on the first machining tool mounting means for movement in the Y-axis relative to the support within a range of motion. The machining tool mounted in the second machining tool mounting means.
Also provided are first drive means for the support to move the support in the Y-axis over the worktable, second drive means for the first machining tool mounting means to move the first machining tool mounting means in the X-axis along the support, and third drive means for moving the second machining tool mounting means in the Y-axis relative to the first machining tool mounting means. A computer control is provided to effect operation of the first and second drive means to move the machining tool in X and Y axes to machine a workpiece supported on the worktable and to effect operation of the third drive means for rapid movement of the machining tool in the Y-axis.
Generally, the support is a bridge member spaced above and extending transversely of the worktable, and the machining tool is supported on the second machining tool mounting means for vertical movement in a Z-axis. The machine tool includes fourth drive means for moving the machining tool in the Z-axis, and the computer control also effects operation of the fourth drive means.
The computer control includes means for determining whether a desired length of movement in the Y-axis is within the range of motion of the second machining tool mounting means on the first machining tool mounting means so as to effect the desired movement by the third drive means in the Y-axis. Preferably, the computer control also includes means for determining whether a desired length of movement in the Y-axis is beyond the range of motion of the second machining tool mounting means and for effecting the desired movement of the machining tool in the Y-axis by operation of the first drive means to move the support and by operation of the third drive means to move the second machining tool mounting means. The computer control desirably may include means for effecting a large displacement of the support in the Y-axis to reposition the machining tool relative to the workpiece and thereafter for effecting a smaller displacement of the second machining tool mounting means in the Y-axis to effect the machining of the workpiece in the Y-axis.
The machining tool may be a laser cutting head, and the machine tool is desirably mounted in a housing providing the second machining tool mounting means and slidable on guides supported on a transverse axis housing providing the first machining tool mounting means and which is movable on the support in the X-axis.